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I'm not sure about the belkin one, but the new MBP can fit in the incase sleeves that they sell right now at the Apple Store. I'm pretty sure it's the old one that was designed for the previous gen MBP so it's somewhat of a tight fit but it still provides the same protection nonetheless.
 
Pretty much any standard 15.4" screen sleeve would work.

I went to Wal-Mart and picked up a cheapo $10, and it works perfectly fine.
 
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